Wednesday, July 13, 2011

Meeting of Positive, and Negative

A still life shown as a Diffusion Transfer Reversal print  (with a  reagent streak) above its companion, a scanned and reversed negative. Two-minute processing time, ISO 100, shot on a Speed Graphic fitted with a Xenotar 150mm f2.8 set to about f11.

This image was made with a NEW55 single PN assembly having a target retail of $6-7 exposed and processed in a Polaroid 545 holder. After exposure, the assembly is pulled normally through the rollers and timed, after which it is opened and peeled apart, revealing the positive print, above.

The negative is separated from the assembly and dropped in ordinary hypo for a few minutes, which makes the spread reagent curl away, and separate from the surface of the emulsion, and also clears any uncleared, unexposed edges where the reagent may have missed. Normally, the reagent covers the entire negative.  The negative is then washed and dried in ordinary water.


This process is quite similar to that of T55 except no sodium sulfite bath is required, and easy to get hypo (fixer) is used. We used Ilford Rapid Fixer, but any solution of sodium thiosulfate will work fine. 
Two aspects are apparent and important: The first, both positive and negative have the same effective speed, though the scanned appearance and dynamic range of positive and negative are different, as expected. The other is that after the two minute process, there is still some residual development activity available on the negative side. This does not affect the positive but results in some solarization of the negative if exposed to room light. We expect to reduce this by optimizing the processing time and the balance of chemicals in the reagent, so they will be essentially self terminating, while still allowing artistic control of the negative, especially the prized delicate edge effects, if the user wants.
We do not know what the archival properties will be from this process but expect with reasonable washing, the negative will last as long as any other conventional negative.

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